Vertical magnetic head having a magnetic circuit with a non-embedded part and having an integrated coil surrounding the non-embedded part

ABSTRACT

Magnetic head for use in magnetic recording and including an integrated coil having at least one winding around a non-embedded part of the magnetic circuit. The winding includes a lower sheet of conductors placed in a chamber etched in the substrate and which is integrated into this substrate. The magnetic head is manufactured in a process including forming on a solid substrate a magnetic circuit with a first and second polar part having embedded portions positioned side by side and separated by a nonmagnetic air gap. The magnetic circuit includes at least one non-embedded bridging part no portion of which is embedded in the substrate. A conductor coil is formed around the non-embedded part of the circuit by making a lower sheet of conductors passing underneath the non-embedded bridging part and by embedding the lower sheet in at least one chamber made in the substrate, and by making an upper sheet of conductors astride the non-embedded bridging part of the magnetic circuit.

DESCRIPTION

1. Technical Field

The present invention relates to a vertical magnetic head withintegrated coil and its manufacturing process.

It finds privileged application in video recording by the generalpublic. But it may also be used in other areas, such as data backup orcomputer memories.

2. State of the Prior Art

A magnetic recording medium for video recording, data backup or computermemory comprises numerous tracks on which information is written in theform of magnetic fields.

To increase information density, not only can the amount of informationper unit length be increased, but also the number of tracks. To achievethis purpose, track width is reduced and, simultaneously, the distancebetween them is reduced until the tracks abut one another.

To avoid any crosstalk problems on reading, the information on twoadjacent tracks is written at opposite angles. The head angle must bemost precise (for example 20±0.150° in the new so-called DVC standardfor <<Digital Video Cassette >>).

To meet these requirements, so-called <<sandwich >> heads can becurrently found on the market of which an example of embodiment isillustrated in FIG. 1 appended hereto. The head shown comprises asubstrate 2 carrying a magnetic circuit 4 made up of a magnetic layerplaced on the top surface of the substrate, this circuit having twopolar parts 5 and 7 at the front separated by an air gap 6 which isformed by a nonmagnetic spacer. This head also comprises, above themagnetic circuit, a nonmagnetic superstrate 2'. An opening 8 is piercedthrough the whole unit to allow the passage of a conductor coil 9surrounding the magnetic circuit.

The head shown in FIG. 1 is intended to co-operate with a recordingmedium S oriented perpendicular to the substrate (in other wordsparallel to the latter's edge).

Such heads may be described as <<vertical >> in the sense that theactive surface is perpendicular to the general surface of the substrate.

The width of the air gap, called 1, is calculated perpendicular to thesubstrate (parallel to the recording medium). This width 1 substantiallycorresponds to the respective width of the tracks in the medium. Thelength of the air gap, called L, is calculated in the direction of therelative movement of the head and recording medium. The height of theair gap, called h, is calculated parallel to the surface of thesubstrate carrying the magnetic circuit.

As soon as track width becomes narrow (less than approximately 10micrometers), these heads become very difficult to fabricate (problemsrelating to precision alignment of the two polar parts during glasswelding, low efficiency due to magnetic circuit length, difficult coilproduction, which is an added part and cannot be adapted easily to apackage production process etc.)

The abstract of Japanese patent, vol. 13, n°98 (P-840) (3446) of Mar. 8,1989, describes a different magnetic head with planar coiling. This headis shown in FIG. 2 appended hereto. It comprises two polar parts 12a,12b separated by an air gap 13, a twin spiral coil 14a, 14b placed overthe two limbs of the magnetic circuit, two connection pads 15a, 15b anda magnetic bridge 15 closing the magnetic circuit.

This head still has disadvantages connected firstly with its coilstructure which is long and therefore resistant producing thermal noiseand, secondly with its magnetic circuit which is relatively long andtherefore has reduced efficiency.

EP-A-0,467,263 discloses a head which partly avoids these drawbacks.This type of head can be seen in appended FIGS. 3 and 4. They show anonmagnetic substrate 21, a first insulating layer 22, a secondinsulating layer 29, a magnetic circuit 30, a conductor coil 38 ofsolenoid type wound around the magnetic circuit, electric connectionstrips 33 and connection pads 34.

FIG. 4 also shows the two front polar parts 25 and 27 separated by anair gap g. Also, an insulating layer 35 covering the entire unit and aprotective layer 36 or superstrate complete the unit and make thecontact surface symmetrical with the recording medium.

Although satisfactory from certain viewpoints, this structure has thedisadvantage of giving rise to a very large head thickness in the zonelying between substrate 21 and superstrate 36. Such thicknesscorresponds to the lower part of coil 38, polar parts 25, 27 andinsulating layers 22, 29, 32, 35. This thickness may give rise tofriction problems with the recording medium leading to problems ofdifferential wear of the various materials. Moreover, this largethickness gives rise to a considerable risk of delamination or bulgingowing to intrinsic constraints in the layers, constraints of thermalorigin etc.

Also, the process for manufacturing a head in accordance with FIGS. 3and 4 is hardly compatible with package processes, in particular for theproduction of the azimuth for the air gap using a diamond instrument, orfor certain planarization stages of the insulators deposited on largethicknesses of metallic patterns, which leads to problems of stepoverlay with breaks on the edge of the patterns.

The purpose of the present invention is precisely to remedy suchdrawbacks.

DISCLOSURE OF THE INVENTION

For this purpose, the invention suggests integrating part of the coilwinding into the substrate, namely the lower sheet of conductors. Inpractice, the lower sheet is placed in a chamber made in the substrate.In this way, the head thickness can be reduced and, correlatively, theproblems described above come to be solved.

In precise manner, the purpose of the invention is a vertical magnetichead comprising a solid substrate, a magnetic circuit with at least onefirst and one second polar part placed side by side and separated by anonmagnetic air gap, this magnetic circuit comprising at least onenon-embedded part in the substrate, a conductor coil surrounding thatpart of the magnetic circuit which is not embedded in the substrate,this head being characterized in that the conductor coil is formed by alower sheet of conductors placed in at least one chamber made in thesubstrate and by an upper sheet of conductors astride the non-embeddedpart.

According to a first embodiment, the magnetic circuit comprises a rearmagnetic closing part and a first and second side magnetic partmagnetically connected to the rear magnetic closing part and to thefirst and second polar parts respectively, the first and second sidemagnetic parts each forming a non-embedded part of the magnetic circuit,and characterized in that the conductor coil comprises at least onewinding coiled around at least the first and/or second side magneticparts, this winding comprising a lower sheet of conductors passing underthe first and/or second side magnetic parts, this lower sheet beingintegrated into the substrate, and an upper sheet astride the firstand/or second side polar parts.

The side magnetic parts are directly connected to the other componentsof the magnetic circuit (rear closing part and polar parts) or via aninsulating layer of controlled thickness (for example SiO₂ or alumina0.1 to 0.2 μm thick). The use of an insulating layer is preferable forhigh frequency operation.

Advantageously, the polar parts are also integrated into the substrate.

Still preferably, the rear magnetic closing part is also integrated intothe substrate.

If the substrate is not in insulating material, either because it isconductive or semi-conductive, the integration of the lower sheet ofconductors can be achieved by etching said chambers in the substrate,said chambers being filled with insulating material in which theconductors are subsequently fabricated. This is the case in particularfor a silicone substrate.

In another embodiment, the magnetic circuit comprises a rear closingpart forming the non-embedded part of the circuit, and the conductorcoil comprises a winding coiled around this rear closing part, with alower sheet of conductors passing under the rear closing part, thislower sheet being embedded in the substrate, and an upper sheet passingover the rear closing part.

Advantageously, the rear closing part is magnetically connected to thefirst and second polar parts, there being no side magnetic parts.

In this alternative, the first and second polar parts may be embedded inthe substrate.

According to a further embodiment, the first and second polar parts formthe part of the magnetic circuit that is not embedded in the substrate,and the conductor coil surrounds at least one of the said first andsecond polar parts, this conductor coil comprising a lower sheet ofconductors passing under at least one of the polar parts and beingembedded in the substrate, and an upper sheet of conductors astride atleast one of the polar parts.

A further object of the present invention is a process for manufacturinga vertical magnetic head such as just described. This process consistsof, on a solid substrate, forming a magnetic circuit with a first andsecond polar part placed side by side and separated by a nonmagnetic airgap, this magnetic circuit comprising at least one part non-embedded inthe substrate, and of forming a conductor winding around thenon-embedded part of the circuit, this process being characterized inthat said conductor winding is formed by making a lower sheet ofconductors in at least one chamber made in the substrate and passingunder the non-embedded part, and by embedding this lower sheet in thesubstrate, and by forming an upper sheet of conductors astride thenon-embedded part of the magnetic circuit.

The process of the invention comprises the methods of use correspondingto the modes of embodiment of the head (forming a magnetic circuit withonly one rear closing part, or with no rear part).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1, already described, illustrates a known magnetic head of sandwichtype;

FIG. 2, already described, illustrates a known magnetic head with planarwinding;

FIG. 3, already described, is a further illustration of a known magnetichead with solenoid winding;

FIG. 4, already described, is another view of the preceding head;

FIG. 5 shows the initial substrate in an example of the process of theinvention;

FIG. 6 gives a longitudinal section view of the production stage of afirst chamber;

FIG. 7 shows the depositing stage of an insulating layer;

FIG. 8 is another longitudinal view of the growth stage of a dualmagnetic layer;

FIG. 9 gives a longitudinal view of the first polar part obtained;

FIG. 10 shows the same first polar part as seen from above;

FIG. 11 shows the formation of a second chamber;

FIG. 12 gives a section view of a second polar part;

FIG. 13 shows a top view of both polar parts and the rear magnetic part;

FIG. 14 gives a cross section view of one of the front polar parts andthe rear magnetic closing part;

FIG. 15 illustrates the etching stage of a chamber for the lower sheetof conductors of the coil;

FIG. 16 shows the filling of a chamber with an electric insulator;

FIG. 17 gives a cross section view of the lower sheet of conductors andthe mask for the magnetic contact lead;

FIG. 18 shows the sub-unit obtained at this stage, as seen from above,with its two polar parts, rear magnetic closing part and lower sheet ofconductors;

FIG. 19 gives a cross section view of a side magnetic part of themagnetic circuit;

FIG. 20 gives a top view of the sub-unit obtained at this stage;

FIG. 21 is a cross section view of the production stage of the electricconnection pads;

FIG. 22 is a close-up top view of these electric connection pads;

FIG. 23 is a cross section view of the production stage of the uppersheet of conductors;

FIG. 24 is a close-up top view of these upper conductors;

FIG. 25 is a section view of the production stage of the contact pads ofthe conductor coil;

FIG. 26 is a top view of the head obtained in accordance with thisembodiment;

FIG. 27 illustrates an alternative with cross orientation ofmagnetization;

FIG. 28 illustrates another embodiment in which the magnetic circuitonly comprises two non-integrated polar parts with a winding coiledaround one of the polar parts;

FIG. 29 illustrates a further embodiment in which the magnetic circuitcomprises two polar parts and a non-integrated rear closing part, thewinding being coiled around this rear closing part;

FIG. 30 illustrates the same embodiment but with a different shaped rearclosing part.

DETAILED DESCRIPTION OF EMBODIMENTS

With reference to FIGS. 5 to 27 a description follows of a firstembodiment of the magnetic head in of the invention. Needless to say,the materials described and the sizes given are only given forexplanatory purposes and are in no way restrictive.

In the particular embodiment described, the starting point is a solidsubstrate in silicon 40, having a crystal orientation of <110> (FIG. 5).Any other crystal orientation may be used to vary the head azimuth. Alayer of insulating material 42 in SiO₂ or Si₃ N₄ is deposited on thissubstrate using the LPCVD method (Low Pressure Chemical VaporDeposition). This insulating layer 42 may have a thickness of 40 nm (or0.04 μm). Using a lithographic process, the shape of the first polarpart is outlined and various reference marks made. Layer 42 issubsequently etched and anisotropic etching of the substrate is made forexample using a KOH solution which produces a first chamber 44 (FIG. 6)of which one side is vertical in this case along the <111> siliconplanes. Layer 42 which served as a mask is then removed.

Thermal oxidization is then carried out to form a layer 46 of SiO₂ (FIG.7). This layer may be 0.2 μm thick.

A magnetic material is then placed in the chamber. Electrolytic growthmay be used for example. For this purpose, a conductive sub-layer isdeposited by cathode sputtering, for example in NiFe with a thickness of0.1 μm. Through a first lithographic process, a mask is formed forexample in resin having an opening opposite the sub-layer placed on thebottom of the chamber. Electrolysis of NiFe is then carried out forexample in a magnetic field to obtain a magnetic layer having magneticdomains oriented parallel to the air gap. The resin is then removed.

This may be conducted in two operations, so that an insulating layer anda conductor sub-layer may be positioned in between the two magneticlayers to improve high frequency performance. For example, for a totalpolar part thickness of 6 μm, two layers of NiFe can be made (includingthe conductor sub-layers of NiFe) each 3 μm thick, separated from aninsulating layer of SiO₂ or Si₃ N₄ or Al₂ O₃ 0.1 μm thick. Two suchmagnetic layers are referenced 48₁ and 48₂ in FIG. 8.

Mechanical polishing is then carried out, stopping at layer 46 to obtaina first polar part 50₁. This part is shown in cross section in FIG. 9and a top view is given in FIG. 10.

On the sub-unit obtained a second insulating layer is deposited, forexample in SiO₂ having a thickness of 0.2 μm. An opening is outlinedwith lithography, and using the layer of SiO₂ obtained and the remainderof layer 46 as a mask, a second chamber 52 is etched out (FIG. 11)isotropically, for example using hyperfrequency plasma to obtain goodselectivity in relation to the silicon oxide. By etching the secondchamber 52, a rear chamber is etched out at the same time which is notseen in FIG. 11 but which will be seen in later Figures, in particularin FIG. 13. The mask and that part of layer 46 remaining on the surfaceare then removed and a magnetic material is deposited in the secondchamber 52 and in the rear chamber. Electrolytic growth of NiFe may beused as previously, in one or two layers separated by an insulatinglayer.

This sub-unit is mechanically polished until the vertical part ofinsulating layer 46, which will form air gap 46, becomes visible. Bothpolar parts 50₁ and 50₂ are then obtained such as they are shown incross section in FIG. 12. FIG. 13 is a top view of these same polarparts 50₁ and 50₂ separated by air gap 46, and also shows the rearmagnetic part 60 which will serve to close the magnetic circuit.

With FIG. 13 it is also possible to illustrate the types of sectionwhich are used in the present description, namely a so-calledlongitudinal section along line AA passing through the polar parts, anda so-called cross section along line BB passing through one of the polarparts (in this case the second 50₂) and the rear magnetic closing part60. The sections which have just been described are all longitudinalsections along AA. The following descriptions will all refer to crosssections following line BB.

FIG. 14 therefore shows the cross section of the sub-unit obtained atthis stage of the process with the second polar part 50₂ and the rearmagnetic closing part 60.

Subsequently (FIG. 15) two side chambers are fabricated between thepolar parts and the rear magnetic closing part 60 (only chamber 62₂ isvisible in the section shown in FIG. 15). Etching may be made inradiofrequency plasma mode. The depth of the chambers may be 4 μm forexample.

If the substrate is not insulating, which is the case in the describedexample in which the substrate is in silicon, an insulating material issubsequently deposited in the chambers, silica for example by PECVD(Plasma Enhanced Chemical Vapor Deposition) and the sub-unit is thenpolished, mechanically for example. This planarization may be precededby a trimming operation made by etching to limit the amount ofinsulating surface to be planarized. FIG. 16 shows the planarizedinsulating material 64 filling the chamber.

In said insulating layer 64 parallel grooves are etched, for example byplasma etching, to a depth of 3 μm. A sub-layer of CrCu is thendeposited by cathode sputtering for example, and using electrolysis thegrooves are filled in for example with copper. FIG. 17 gives a crosssection view of the conductors 66 obtained in these grooves. They formtwo lower sheets 66₁ and 66₂ visible in FIG. 18 which is a top view ofthe sub-unit. These two lower sheets extend between polar parts 50₁ and50₂ and rear magnetic closing part 60.

The sub-unit is then covered with an insulating layer 70 that can beseen in FIG. 17, in SiO₂ for example, deposited by PECVD having athickness of 1 μm. This layer is then etched, for example by plasmaetching, to form openings 72₁, 72₂ above polar parts 74₁, 74₂ above theends of the rear magnetic closing part 60. These openings are visible inthe top view given in FIG. 18. Only openings 72₂ and 74₂ are shown insection BB of FIG. 17.

According to one alternative embodiment, an insulating stop layer, forexample in A₂ O₃, 0.2 μm thick, is deposited prior to insulating layer70. This stop layer is exposed by etching layer 70 in openings 72₁, 72₂and 74₁ and 74₂. This stop layer is maintained in the magnetic circuit.

The process continues by fabricating the two magnetic side parts whichwill complete the magnetic circuit. First an insulating layer 80 (FIG.19) having the same thickness as the future side magnetic parts, isdeposited. For example a layer 3 μm thick of SiO₂ can be deposited byPECVD. This layer is etched in both zones in which the two magneticparts are to be formed, namely over the lower conductor sheets 66₁, 66₂already fabricated and over openings 72₁, 72₂ and 74₁, 74₂ already made.Using electrolysis a magnetic material 82₁, 82₂ is then deposited usingoperating methods that have already been described (FIG. 20). Thismaterial may possibly be wafered. For proper orientation of the magneticdomains, electrolysis may be conducted in a magnetic field, thedirection of this field this time being perpendicular to the directionof the air gap.

The sub-unit obtained is illustrated seen from above in FIG. 20 in whichthe two side magnetic parts 82₁ and 82₂ can be seen respectively astridethe two lower conductor sheets 66₁ and 66₂ and forming the junctionbetween rear part 60 and the two polar parts 50₁ and 50₂.

To complete the conductor winding, the process next includes formationof the electric connection pads. An insulating layer 90, for example inSiO₂, (FIG. 21) 1 μm thick is deposited using the PECVD method. Openingsare etched in this layer at the side edges of the two lower sheets ofconductors, etching being sufficiently deep to expose the ends of theconductors. In the example described up until now, it is thereforeassumed that layer 90 is etched over its own height and that of layers80 and 70, that is to say over 3+1+1=5 μm. The openings may be 4 μmwide, separated by a distance of 6 μm. Using the same electrolyticgrowth process, the openings made are filled with a metal, copper forexample, to obtain electric connections 84₂ which come to rest on theends of the conductors of the two lower sheets 66₁, 66₂. FIG. 22 shows atop view of pads 84₂ at the ends located along the inner side edge ofside magnetic part 82₂ which closes the circuit. Similar pads are madeon the outer edge of the same sheet of conductors and on the othersheet.

An upper sheet of conductors is then made by depositing an insulatinglayer 94 having the same thickness as the thickness of the desired sheet(FIG. 23). For example, a 3 μm layer of SiO₂ is deposited by PECVD.Parallel grooves are etched, for example 8 μm wide and 2 μm apart. Thesegrooves extend from one connection pad to another. Again using anelectrolytic growth process, two upper sheets of conductors are formedwhich come to rest, at either end, on the electric connection padsclosing together the two solenoids. FIG. 23 gives a BB section view ofconductors 96₂ at connection pads 84₂ and, in FIG. 24 the complete sheetis shown as seen from above.

During this operation, the conductor material is also deposited whichwill be used to form connections 98₁, 98₂ to connect the ends of thecoil to future contact pads. A top view of these conductors can be seenin FIG. 26. A section view of conductor 98₂ can be seen in FIG. 23.

In this manner a dual winding has been made with two lower sheetspassing under the side magnetic parts and integrated into the substrate,two upper sheets passing over the side magnetic parts, and connectionpads connecting one conductor of one lower sheet to the correspondingconductor of the upper sheet. Needless to say, for these two windings tobe correctly positioned the sheet conductors must be slightly tilted sothat the end of one lower conductor is placed opposite one end of anupper conductor, whose other end is placed opposite the end of the lowerconductor adjacent to the first.

The remaining stage is to make the contact pads providing access to thecoil. An insulating layer 100 is deposited on the whole unit (FIG. 25)having the same thickness as the thickness of the desired pad. Forexample 1 μm of SiO₂ is deposited by PECVD. This insulating layer isetched to expose the end of connections 98₁, 98₂ and pads 102₁, 102₂ aremade, in gold for example, which has good welding properties for thefuture connection wires. Advantageously, pads 102₁ and 102₂ are made byelectrolysis using a previously deposited conductive sub-layer. Assub-layer alloys of CrAu, CrCu and even FeNi may be used. A top view ofconnections 98₁, 98₂ and contact pads 102₁, 102₂ is given in FIG. 26,and a BB section view of connection 98₂ and pad 102₂ is given in FIG.25. FIG. 26 is on a smaller scale than the previous Figures to show theentire head with its active part referenced 120 and its outletconnections.

Over the unit thus obtained a superstrate may possibly be added, insilicon for example, to give symmetry to the contact zone in relation tothe recording medium. This superstrate must not of course mask thecontact pads.

It is of interest to compare known structures described in theintroduction with the structure of the invention. For example, thethickness of the materials contained between the substrate and thesuperstrate are:

i) for a head of the prior art such as described in EP-A-0 467 263:lower coiling in 5 μm of insulator, polar part 6 μm, upper coiling andpads in 5 μm of insulator, i.e. a total insulator thickness of 16 μm;

ii) for a head of the invention: magnetic circuit closed in 4 μm ofinsulator, upper coiling and pads in 5 μm of insulator, i.e. a totalinsulator thickness of 9 μm.

The gain in thickness is therefore evident. The problems of friction,differential wear, intrinsic and thermal constraints in the insulatinglayers are consequently far easier to solve in the invention than in theprior art.

The efficiency and performance at high frequency of the magnetic headwhich has just been described can be further increased by takingadvantage of the magnetic anisotropy, and in particular of theorientation of the domains as shown in FIG. 27. In this Figure, only themagnetic parts of the head are shown, namely polar parts 50₁, 50₂assumed to be made in two layers, side parts 82₁, 82₂ and the rearclosing part 60 also assumed to be made in two layers. The arrowsindicate the orientation of magnetization. In polar parts 50₁ and 50₂and in rear closing part 60 this orientation is parallel to the air gap,whereas in side parts 82₁, 82₂ this orientation follows the axis of easymagnetization, which is perpendicular to the air gap.

In the embodiment which has just been described, the magnetic circuitcomprises two polar parts, two side parts and a rear magnetic closingpart. The invention is not, however, restricted to this embodiment. Onthe contrary, it extends to heads having only two polar parts with noside parts and no rear closing part, or having only two polar parts andone rear closing part. FIGS. 28, 29 and 30 illustrate some of thesepossibilities.

FIG. 28 gives a diagram of a magnetic head which only comprises twopolar parts 50₁, 50₂ and a winding 95 around one of these parts (50₁).Evidently, it is possible to use another winding on the other polar part(50₂). In this (or these) windings, the lower sheet of conductors isintegrated into the substrate.

In this embodiment, the polar parts are not integrated into thesubstrate.

FIG. 29 illustrates another embodiment in which the magnetic circuitcomprises two polar parts 50₁, 50₂ which may or may not be integratedinto the substrate, and a rear magnetic closing part 60 that is notintegrated into the substrate. It is around this rear part that coil 97is wound with a lower sheet of conductors integrated into the substrate.

In this FIG. 29, the rear magnetic closing part 60 is straight, but inFIG. 30 it is horse-shoe shaped. Winding 99 is coiled here around thethree stems of the rear part again with a lower sheet conductorsintegrated into the substrate.

Other embodiments can be imagined that come within the limits of thisinvention, provided that the head comprises two polar parts and at leastone part which is not embedded, the coil being wound around this partand having its lower sheet of conductors integrated into the substrate.

What is claimed is:
 1. Vertical magnetic head comprising a solidsubstrate, a magnetic circuit with at least a first and a second polarpart having embedded portions positioned side by side and separated by anonmagnetic air gap the magnetic circuit comprising at least onenon-embedded bridging part with no portion of there of embedded in thesubstrate, a conductor coil surrounding the non-embedded part,whereinthe conductor coil is formed by a lower sheet of conductors placed in atleast one chamber made in the substrate, underneath the non-embeddedbridging part, the lower sheet being integrated in the substrate, and anupper sheet of conductors astride the non-embedded bridging part. 2.Magnetic head in accordance with claim 1, wherein the magnetic circuitcomprises a rear magnetic closing part and a first and second sidemagnetic part magnetically connected to the rear magnetic closing partand to the first and second polar parts respectively, the first andsecond side magnetic parts each forming the non-embedded bridging partof the magnetic circuit, no portion of said bridging part being embeddedin the substrate, and wherein the conductor coil comprises at least onewinding coiled around at least one of the first and second side magneticparts, the winding comprising the lower sheet of conductors passingunderneath the at least one of the first and second side magnetic parts,the lower sheet being integrated in the substrate, and the upper sheetastride the at least one of the first and second side magnetic parts. 3.Magnetic head in accordance with claim 1, wherein the substrate issemiconductive or conductive, the lower sheet of conductors is placed inthe at least one chamber etched in the substrate and filled with aninsulating material, the conductors of the lower sheet being formed inthe insulating material.
 4. Magnetic head in accordance with claim 2,wherein the first and second polar parts are integrated in the substrateand are placed in a first and second chamber etched in the substrate. 5.Magnetic head in accordance with claim 2, wherein the rear magneticclosing part is also integrated in the substrate and placed in a chamberetched in the substrate.
 6. Magnetic head in accordance with claim 1,wherein the magnetic circuit comprises a rear closing part forming thenon-embedded bridging part of the circuit, and the conductor coilcomprises a winding coiled around the rear closing part, with the lowersheet of conductors passing under the rear closing part, the lower sheetbeing embedded in the substrate and the upper sheet astride the rearclosing part.
 7. Magnetic head in accordance with claim 6, wherein therear closing part is magnetically connected to the first and secondpolar parts.
 8. Magnetic head in accordance with claim 7, wherein thefirst and second polar parts are embedded in the substrate.
 9. Processfor manufacturing a vertical magnetic head, comprising:on a solidsubstrate, forming a magnetic circuit with a first and second polar parthaving embedded portions embedded in the substrate positioned side byside and separated by a nonmagnetic air gap, and at least onenon-embedded bridging part with no portion there of embedded in thesubstrate; and forming a conductor coil around the non-embedded part ofthe circuit, including making a lower sheet of conductors passingunderneath the non-embedded bridge part, embedding the lower sheet in atleast one chamber made in the substrate, and making an upper sheet ofconductors astride the non-embedded bridging part of the magneticcircuit.
 10. Process in accordance with claim 9, wherein said step offorming the magnetic circuit further comprises:forming a rear magneticclosing part and a first and second side magnetic part as thenon-embedded bridging part magnetically connected to the rear magneticclosing part and to the first and second polar parts respectively, andwherein said step of forming the conductor coil includes making at leastone winding coiled around at least one of the first and second sidemagnetic parts, the winding being obtained by making firstly the lowersheet of conductors passing underneath the at least one of the first andsecond side magnetic parts, the lower sheet of conductors beingintegrated in the substrate, and secondly the upper sheet of conductorsastride the at least one of the first and second side magnetic part. 11.Process in accordance with claim 9, wherein the substrate issemiconductive or conductive, wherein said step of forming the conductorcoil comprises,etching the least one chamber in the substrate, fillingthe at least one chamber with an insulating material, and forming theconductors of the lower layer in the insulating material.
 12. Process inaccordance with claim 11, wherein the first and second polar parts arealso integrated into fit substrate by etching a first and second chamberin the substrate.
 13. Process in accordance with claim 11, wherein therear magnetic closing part is integrated into the substrate by placingthe rear magnetic closing part in a chamber etched in the substrate. 14.Process for manufacturing a magnetic head in accordance with claim 9,wherein the step of forming the magnetic circuit comprises forming arear closing part as the non-embedded bridging part on the substrate,andthe step of forming the conductor coil comprises forming theconductor coil around the rear closing part by making the lower sheet ofconductors passing underneath the rear closing part, the lower sheetbeing embedded in the substrate; and making the upper sheet astride therear closing part.
 15. Process in accordance with claim 14, furthercomprising placing the rear closing part in magnetic contact with thefirst and second polar parts.
 16. Process in accordance with claim 15,wherein the first and second polar parts are integrated in thesubstrate.